An Internet protocol (IP) service can include plural items delivered using an IP session. An IP session may include an IP stream carrying primary content, such as live or recorded music, and further IP streams carrying secondary content, such as error correction or song lyrics. Such services can be broadcast in a multiplexed transport stream using terrestrial digital video broadcast, for example DVB-T, ISDB-T or ATSC-T, or DVB-S (satellite), DVB-C (cable) or Digital Audio Broadcasting (DAB) networks.
Wireless IP networks typically serve one or more mobile terminals having stringent power requirements. Such a terminal may be required to operate for lengthy periods on an internal source of power. In the case of simplex broadcast systems supporting unidirectional data delivery, for example DVB-T or DVB-S networks, a large proportion of the power consumption in a terminal is due to the demands of a receiver when receiving data transmissions. It is desirable to conserve power by reducing the amount of data received, i.e. by receiving only selected data.
Selective data reception can be implemented for receiving a particular stream of data in a Time Division Multiple Access (TDMA) transmission by switching the receiver between its on and off states, so that data reception is suspended during time slots relating to services or content that are not required. In our co-pending application, GB0216240.2, a method is disclosed in which a session announcement is transmitted on a first channel in a transport stream. If a service is of interest to a user of the terminal, the information conveyed in the service announcement can be used to control the operation of the receiver in order to selectively receive broadcast or multicast data relating to that service. This information may include the frequency of the broadcast channel carrying a particular service, a description of the service in terms of a category, e.g. news, sport, entertainment, and a sub-category, for example, the sports category may be divided into football, hockey, athletics sub-categories. The information may also include the number of messages containing the relevant content that will be sent and a time out value. When data reception is not required, i.e. when data relating to the selected service is not being transmitted, the receiver is disabled, in order to conserve power.
In another co-pending application, PCT/IB02/04823, a receiver is controlled to selectively receive data using a schedule of delivery time slots, where the schedule is extracted from information relating to the IP address of the content source provided in a session announcement. Tie receiver may be switched off or operated at a lower power between the delivery time slots, when data reception is not required.
The performance of these methods may be improved by grouping related data packets into bursts before their transmission. The transmission takes the form of a sequence of bursts taking up most or all of the available bandwidth for a relatively short period of time, each burst carrying a significant amount of interrelated data. Information relating to the burst duration and the interval between related bursts is encoded into the headers of the data packets in the bursts, while information describing the contents of the burst are signalled using external address mapping functionality provided by the transmission network baseline, such as the network information table (NIT) table in a DVB system. This fisher reduces the period of time for which the receiver is actively receiving data.